Activated metathesis catalysts

ABSTRACT

Process for preparing a supported catalyst (catalyst C) comprising a support (support S) and an active component (activator A), wherein  
     a) a catalyst precursor is prepared by applying an activator customary for the catalysis of metathesis reactions (activator precursor) to a customary support (step a),  
     b) the catalyst precursor prepared in step a) is brought into contact with a hydrocarbon compound at from −20 to 550° C. (step b) and  
     c) the catalyst precursor prepared in step b) is heated at from 410 to 850° C. in an inert gas atmosphere (step c).

[0001] The present invention relates to a process for preparing asupported catalyst (catalyst C) comprising a support (support S) and anactive component (activator A), wherein

[0002] a) a catalyst precursor is prepared by applying an activatorcustomary for the catalysis of metathesis reactions (activatorprecursor) to a customary support (step a),

[0003] b) the catalyst precursor prepared in step a) is brought intocontact with a hydrocarbon compound at from −20 to 550° C. (step b) and

[0004] c) the catalyst precursor prepared in step b) is heated at from410 to 850° C. in an inert gas atmosphere (step c).

[0005] Furthermore, the invention relates to catalysts (catalysts C)which are obtainable by this process and to a process for preparingunsaturated compounds by metathesis using a catalyst (C).

[0006] The metathesis of unsaturated compounds is a long-establishedmethod of breaking and rearranging C—C bonds (e.g. Mol, J. C., Chapt.4.12.2 “Alkene Metathesis” in “Handbook of Heterogeneous Catalysis”,Eds. Ertl, G., Knözinger, H., Weitkamp, J., VCH, Weinheim 1997;Weissermehl, K., Arpe, H.-J., Chapt. 3.4 “Olefin-Metathese” in“Industrielle Organische Chemie”, 4th edition, VCH, Weinheim 1994).

[0007] Various types of catalysts have been described forheterogeneously catalyzed metathesis. For the temperature range up to120° C., the use of supported R₂O₇ or Re(CO)₁₀ catalysts is customary(Mol, J. C., Chapt. 4.12.2 “Alkene Metathesis” in “Handbook ofHeterogeneous Catalysis”, Eds. Ertl, G., Knözinger, H., Weitkamp, J.,VCH, Weinheim 1997). However, rhenium is a rare and relatively expensiveelement, so that the use of such a catalyst is often uneconomical. Atsomewhat higher temperatures up to 400° C., catalysts based on MoO₃,CoO—MoO₃, MoS₂, Mo(CO)₆ or various supported Mo complexes can beemployed according to the literature, and at even higher temperatures upto 540° C., systems based on WO₃, WS₂, W(CO)₆ or supported W complexescan be employed (Mol, J. C., Chapt. 4.12.2 “Alkene Metathesis” in“Handbook of Heterogeneous Catalysis”, Eds. Ertl, G., Knözinger, H.,Weitkamp, J., VCH, Weinheim 1997; Weissermehl, K., Arpe, H.-J.,Chapt.3.4 “Olefin-Metathese” in “Industrielle Organische Chemie”, 4th edition,VCH, Weinheim 1994; Heckelsberg, L. F., Banks, R. L., Bailey; G. C.,Ind. Eng. Chem. Prod. Res. Develop. 8 (1969), 259-261). Although theseare very inexpensive, they generally have a significantly lower activityand also display lower selectivities. The reduced selectivities are aconsequence of double bond isomerization which proceeds in parallel tometathesis over the strongly acidic molybdenum and tungsten compounds atrelatively high reaction temperatures, which leads to the formation ofundesirable products.

[0008] To suppress the secondary reaction of double bond isomerization,U.S. Pat. No. 3,586,731 describes the addition of alkali metal salts oralkaline earth metal salts to silica-supported oxides, sulfides orhexacarbonyls of tungsten, molybdenum or rhenium. However, this can leadto a considerable decrease in the catalyst activity.

[0009] U.S. Pat. No. 4,024,201 proposes adding halogen-containingcompounds or amines to the feed. to a supported WO₃ catalyst. However,such polar compounds are at the same time known as catalyst poisons inmetathesis, so that a greatly reduced activity may also be expectedhere.

[0010] It is an object of the present invention to prepare a catalysthaving increased metathesis activity and selectivity.

[0011] We have found that this object is achieved by the process andcatalysts defined at the outset.

[0012] The catalyst precursors which are prepared in step a) and aresubsequently reacted further in steps b) and c) to give the catalysts Cof the present invention are the supported catalysts customarily used inmetathesis reactions. Such catalysts are described, for example, in“Handbook of Heterogeneous Catalysis”, edited by G. Ertl, H. Knözingerand J. Weitkamp, Volume 5, VCH Verlagsgesellschaft mbH, Weinheim,Chapter 4.12.2, Alkene Metathesis, pages 2387 to 2399.

[0013] Possible supports (support S) for the preparation of catalystprecursors are all materials customarily used for the preparation ofsupported catalysts, for example metal oxides, nitrides, borides,carbides, silicates, activated carbon, graphite. Preference is given tocompounds of main group elements or elements of transition group VI or11 and also mixtures of the abovementioned compounds. Particularpreference is given to Al₂O₃, aluminosilicates, Ga₂O₃, SiO₂, GeO₂, TiO₂,ZrO₂, SnO₂ and mixtures of the abovementioned compounds. Suitablesupports typically have a specific surface area of 10-500 m²/g,preferably 100-400 m²/g. The preferred pore volume (determined by meansof mercury porosimetry) is from 0.3 to 1.3 ml/g. The preferred waterabsorption is from 0.5 to 1.5 mug. The supports are usually shapedbodies such as spheres, granules, extrudates or pellets. The support mayhave additionally been pretreated with acids.

[0014] The active components (activator precursors) applied to thesupport (S) in step a) include the customarily used compounds andmixtures thereof. These are generally compounds of the metals oftransition groups V, VI and VII, in particular compounds of rhenium,tungsten or molybdenum. Possible compounds are the sulfides, oxides,nitrides, carbides, oxycarbides, carbonyls, organic complexes, halides,acids, polyacids, heteropolyacids and salts of the acids, polyacids andheteropolyacids. Such salts are preferably alkali metal or ammoniumsalts. In the present context, organic complexes are, for example,dialkyl complexes, acyl compounds, acetylacetonates or allyl complexes.Particular preference is given to molybdenum oxide and tungsten oxide.The term salts also includes substoichiometric bronzes. The term oxideextends not only to the stoichiometric compounds such as MoO₃, WO₃, MoO₂and WO₂ but also includes substoichiometric phases of the type MO₃₋₂. Assupport for tungsten or molybdenum compounds, very particular preferenceis given to SiO₂.

[0015] In general, the preparation of the customary catalysts comprisingoxides as activator precursors and serving as catalyst precursors iscarried out in step a) by impregnating the support S with a solution ofthe abovementioned compounds. In the case of tungsten oxide, a solutionof, for example, ammonium metatungstate, tungstic acid or tungstenpentachloride can be employed for this purpose. The impregnated supportsare then usually dried in air at from 100 to 200° C. for a number ofhours. This is usually followed by a calcination step. For this purpose,the impregnated and dried supports are usually heated in anoxygen-containing gas atmosphere, e.g. in air, at from 400 to 850° C.for a period of from about half an hour to 5 hours. The catalystprecursors prepared in this way can also be pretreated by means ofheating steps in inert gas, for example N₂, CO₂ or noble gases, or bepartially reduced in reducing gas mixtures comprising, for example,hydrogen, CO, ammonia or hydrazine.

[0016] To prepare the customary supported catalysts with carbides oroxycarbides as activator precursors which are included among thecatalysts precursors, it is usual to start from the catalyst precursorscomprising oxides as active component which have been prepared by theabove method. In the carbiding step, the appropriate catalyst precursorscomprising metal oxide are heated at from 550 to 800° C. in ahydrocarbon-containing stream, e.g. a methane stream, in the presence ofhydrogen for, in general, a number of hours. The preparation of tungstencarbides typically requires temperatures about 50-200° C. higher thanthose for preparing molybdenum carbides. The properties of the carbidesare also influenced by the H₂/CH₄ ratio which is typically 80/20. Theappropriate carbiding methods are known and described, for example, inOyama, S. T., Catal. Today, 15 (1992), 179.

[0017] After the carbiding step, these catalyst precursors have to bestored under an inert gas atmosphere because of their sensitivity toair, or they are passivated by means of dilute oxygen and thenreactivated in the synthesis reactor. A further possibility is takingout the freshly prepared carbides under a liquid which substantiallyprotects the carbide surface from atmospheric oxygen.

[0018] Furthermore, the following processes are also suitable forpreparing catalyst precursors comprising carbides as activatorprecursors:

[0019] In J. Catal. 128, 126 (1991), Lee et al. describe the preparationof Al₂O₃-supported molybdenum carbides by (i) reduction followed bycarbiding, (ii) direct carbiding in CH₄/H₂ or (iii) nitriding by meansof NH₃ followed by carbiding.

[0020] Volpe, Boudart, J. Solid State Chem. 59, 332 (1985) and Volpe,Boudart, J. Solid State Chem. 59, 348 (1985) describe thenitriding/carbiding of MoO₃ and WO₃ in more detail.

[0021] The reduction of MoO₃ on carbon supports by means of hydrogen,which is coupled with carbiding by the carbon support above 530° C., isdescribed, for instance, in Liang et al., Chem. Mater. 2002, 14, 3148.

[0022] Oxycarbides which can be used as activator precursors aredescribed, for example, in Pham-Huu et al., Appl. Catal. A 132 (1995),77. They can be prepared from the oxides by only partial carbiding. Theoxycarbides are also formed under suitable conditions during thereaction when the oxide is used as starting material and ahydrocarbon/H₂ mixture is then passed over the catalyst at elevatedtemperatures (for instance: H₂/n-hexane=150, T=350° C.

[0023] The oxycarbides can also be prepared by treatment of carbideswith oxygen. In Ledoux et al., New Frontiers in Catalysis, 1993, p. 955,Guczi, L. et al. (editors), Elsevier Science Publishers B.V., thecarbide is firstly treated with air at 350° C. and then with hydrogen atthe same temperature.

[0024] In step b), the catalyst precursors which have been prepared inthis way are brought into contact with a hydrocarbon compound. Suitablehydrocarbon compounds are, in particular, aromatics, alkanes,cycloalkanes, alkynes, cycloalkynes, olefins or cycloolefins having from1 to 20 carbon atoms. Particular preference is given to C₃-C₁₂-olefins,very particularly preferably butenes and octenes, e.g. 1-butene andn-1-octene.

[0025] In the treatment of the catalyst precursor with the hydrocarboncompound, the latter can be either in liquid or gaseous form. Thetreatment time is not critical and is usually 1 min-24 h, preferably 5min-4 h. The temperature during the treatment is generally from −20 to550° C., but is not critical. The latter also applies to the pressure,which is generally from 0.5 to 40 bar.

[0026] The catalyst precursor which has been treated with thehydrocarbon is subsequently heated to from 410 to 850° C., preferablyfrom 500 to 850° C., in an inert gas atmosphere in step c). Suitableinert gases are, in particular, nitrogen, CO₂ and the noble gases. Thetreatment in step c) is usually carried out for from 5 minutes to 100hours, preferably from 30 minutes to 24 hours, with the pressure onceagain being noncritical and usually being from 0.5 to 40 bar.

[0027] The catalysts (C) of the present invention may further comprisepromoters. These are generally cobalt, alkali metal or alkaline earthmetal compounds. They are generally applied to the catalyst by addingappropriate salts, e.g. nitrates or hydroxides, to the impregnationsolutions for preparing the catalyst precursors, or by doping thecatalysts afterward with an appropriate impregnation solution andcalcining the catalysts once again to immobilize the dopant.

[0028] The proportion of activator (A) in the catalyst (C) is usuallyfrom 0.1 to 30% by weight.

[0029] The catalyst (C) particularly preferably comprises WO₃ intetragonal form, as activator (A) and SiO₂ as support (S).

[0030] The catalysts of the present invention are particularly usefulfor the metathesis of unsaturated compounds such as alkenes or alkynes.Such processes are generally known and are described, for example, in“Industrielle Organische Chemie”, Klaus Weissermel, Hans-Jürgen Erpel,5th edition, Wiley, VCH, 1998, Chapter 3.4 and “Handbook ofHeterogeneous Catalysis”, edited by G. Ertl, H. Knözinger and J.Weitkamp, Volume 5, VCH Verlagsgesellschaft mbH, Weinheim, Chapter4.12.2, Alkene Metathesis, pages 2387 to 2399. However, they can also beused for the metathesis of unsaturated esters, nitriles, ketones,aldehydes, acids or ethers, as described, for example, in Xiaoding, X.,Imhoff, P., von den Aardweg, C. N., and Mol, J. C., J. Chem. Soc., Chem.Comm. (1985), p. 273. In the reaction of substituted olefins, use isfrequently made of a cocatalyst, for example tin, lead or aluminumalkyls, to increase the activity further.

[0031] The catalysts (C) of the present invention can be used in thesame way as the known metathesis catalysts which are prepared asdescribed in step a) of the process of the present invention and serveas catalyst precursors for the catalysts C of the present invention.

[0032] The catalysts of the present invention can be particularlyadvantageously used in metathesis processes for preparing propene bymetathesis of a mixture comprising 2-butene and ethylene or 1-butene and2-butenes, or for preparing 3-hexene and ethylene by metathesis of1-butene. Appropriate processes are described in detail inDE-A-19813720, EP-A-1134271, WO 02/083609, DE-A-10143160.

[0033] The abovementioned C₄ starting compounds are usually supplied inthe form of a raffinate II. The raffinate II is a C₄ fraction whichgenerally has a butene content of from 30 to 100% by weight, preferablyfrom 40 to 98% by weight. Apart from butenes, saturated C₄-alkanes inparticular can also be present. The way in which such raffinates 11 areobtained is generally known and is described, for example, inEP-A-1134271.

[0034] In particular, it is possible to use 1-butene which is obtainedby distilling off a 1-butene-rich fraction from raffinate II. 1-Butenecan likewise be obtained from the remaining 2-butene-rich fraction bysubjecting the 2-butene-rich fraction to an isomerization reaction andsubsequently fractionally distilling the product to give a 1-butene-richfraction and a 2-butene-rich fraction. This process is described inDE-A-10311139.

[0035] The rhenium-containing catalysts of the present invention areparticularly useful for reactions in the liquid phase at from 10 to 150°C. and a pressure of from 5 to 100 bar.

[0036] The tungsten- or molybdenum-containing catalysts of the presentinvention are 5 generally used in gas-phase reactions. The temperaturehere is generally from 150 to 500° C. The pressure is generally 5-50bar.

[0037] Experimental Part

[0038] A. Preparation of the Catalysts

[0039] A. 1. Preparation of the Catalyst Precursors

EXAMPLE 1 Preparation of WO₃/SiO₂ catalyst—cats A—E

[0040] SiO₂ supports were in each case impregnated with aqueous, diluteammonium metatungstate solution to incipient wetness. The extrudateswere then dried at 120° C. in a drying oven for 16 hours. The catalystwas finally treated under the conditions indicated in a rotary tubefurnace and cooled under dry nitrogen (20 I/h). The catalyst C1 was thenadditionally impregnated with a 0.5 M NaOH solution and once again driedand calcined under the abovementioned conditions, as a result of whichthe Na content in the finished catalyst was increased from 1 100 to 4500 ppm (=sample C2). Further details regarding the preparativeconditions and the catalyst precursors themselves are given in table 1.TABLE 1 WO₃ content Conditions in rotary tube Cat [wt %] Support furnaceA 12.1 BASF D11-10, 1.5 mm extrudates 1 h in air (20 l/h), 593° C. (171m²/g) B 13.9 BASF D11-10, 1.5 mm extrudates 1 h in air (20 l/h), 593° C.(171 m²/g) C1 12.5 BASF D11-10, 1.5 mm extrudates 1 h in air (20 l/h),593° C. (171 m²/g) D 11.2 Shell X970 CY, 3 mm extrudates 1 h in air (20l/h), 593° C. (326 m²/g) E1 15.0 Solvay Siligel BR 5155/1, 0.8-2 mm 1 hin air (20 l/h), 593° C. spheres (350 m²/g) E2 15.0 Solvay Siligel BR5155/1, 0.8-2 mm 1 h in air (20 l/h), 593° C. + 2.5 h spheres (350 m²/g)in N₂ (20 l/h), 850° C. F 12.2 BASF D11-10, 0.5-0.8 mm granules 1 h inair (20 l/h), 593° C. (171 m²/g)

EXAMPLE 2 Preparation of the Tungsten Carbide Catalyst—Cat G

[0041] To prepare catalyst G, 70 ml of the WO₃/SiO₂ catalyst A wereplaced in a glass reactor through which gas was passed from the topdownward. The glass reactor was heated from the outside by means of anelectric furnace, and the catalyst bed was located approximately in themiddle of the heating zone on a glass frit. After the catalyst had beeninstalled and the reactor had been closed, the plant was firstly flushedwith nitrogen (30 min, 20 I/h). A gas stream comprising 3.9 I/h ofmethane and 15 I/h of hydrogen were subsequently passed over thecatalyst. The reactor was then heated to 750° C. over a period of 180minutes and held at 750° C. for 6 hours. It was then cooled to 500° C.over a period of 1 hour and this temperature was held for 2 hours. Thereactor was then cooled and the methane/hydrogen stream was replaced bya stream of nitrogen. After the reactor had been flushed, the reactorinlet and outlet were closed and the reactor was removed from the plantin such a way that the catalyst could be transferred into a glove boxwithout coming into contact with air. Contact with air was likewiseavoided in subsequent handling of the catalyst, for instance theinstallation of the catalyst in the reactor or its introduction intoanalytical instruments.

[0042] An XRD (X-ray diffraction) pattern of the catalyst removed fromthe reactor after the metathesis reaction shows the compounds WC and W₂Ctogether with traces of metallic tungsten. WOx compounds are notobserved.

EXAMPLE 3 Preparation of an MoO₃/SiO₂ Catalyst—Cat H

[0043] SiO₂ (BASF D11-10, 1.5 mm extrudates) was impregnated with anaqueous, dilute solution of (NH₄)₆Mo₇O₂₄*4H₂O to incipient wetness. Theextrudates were then dried at 120° C. in a drying oven for 16 hours. Thecatalyst was finally calcined at 593° C. in air (20 I/h) for 1 hour in arotary tube furnace and cooled under dry nitrogen. The MoO₃ content was11.1% by weight.

EXAMPLE 4 Preparation of a WO₃/SiO₂ Catalyst—Cat J

[0044] 508.2 g of SiO₂ (Shell X970 CY, 3 mm extrudates) were predried at500° C. (air, 50 I/h). The cooled extrudates were impregnated with asolution of 70 g of WCl₆ in 1 200 ml of ethanol under a nitrogenatmosphere. The catalyst was subsequently dried in a stream of air (300I/h, about 30 min) and calcined at 550° C. in air (50 I/h) for 2 hours.The catalyst was subsequently heated for another 2 hours at 850° C.under N₂ (50 I/h). The WO₃ content was 7.3%.

[0045] A.2 Activation of the Catalyst Precursors from Steps b) and c)

EXAMPLE 5 Activation of the Catalysts (Methods 0-VII)

[0046] The catalysts were, with the exception of the compartive methods0 and VII, each firstly brought into contact with a hydrocarbon, eitherdirectly in the reactor or by wetting with a liquid before installationof the catalyst. The catalysts which had been moistened withhydrocarbons were, with the exception of the comparative methods 0 andVI, subsequently heated under flowing nitrogen (30 I/h) to thetemperature indicated for the time indicated and subsequently cooled tothe reaction temperature under nitrogen. The conditions are reported indetail in table 2. TABLE 2 Time for which the hydrocarbon Heat is T(heat treatment allowed to treatment)¹⁾ time Method Hydrocarbon T(wetting) [° C.] act [° C.] [h] 0 (comp.) Not Not Not Not Not applicableapplicable applicable applicable applicable I (comp.) 1-Butene 190¹⁾  3h 300 18 II (comp.) 1-Butene 190¹⁾  3 h 400 17 III 1-Butene 190¹⁾ 3-5 h510 16-20 IV n-1-Octene Room temp.  10 min 510 15 V n-Octane Room temp. 10 min 510 15 VI (comp.) n-1-Octene Room temp.  10 min Not Notapplicable applicable VII (comp.) Not Not Not 510 17 applicableapplicable applicable

[0047] In-situ XRD measurement on catalysts F/0 and F/IV

[0048] Measurement on Catalyst F/0

[0049] Catalyst F/0 is a catalyst of the prior art and was prepared asdescribed under point A.1, example 1 (method 0 in table 2). The catalystF/0 was pulverized. The sample was introduced into the XRD measurementchamber on a heated alumina plate (depth: 0.8 mm). The measuringinstrument is a model D8 Advance (from Bruker/AXS) equipped with aheated camera HTK 1200 from Paar. The measurement was carried out usingCu-K_(α) radiation in θ/θ geometry with a primary- and secondary-sideGöbel mirror in the range 2θ=15°−52° at 6s/step at selectedtemperatures.

[0050] At room temperature, the sample in each case comprised monoclinicWO₃ and amorphous SiO₂ (FIG. 1). The sample was heated in air. At 400,500 and 600° C., no change was observed. Only at 850° C. did tetragonalWO₃ form. The sample was then cooled to 200° C., resulting in the WO₃transforming back into the monoclinic phase.

[0051] Measurement on catalyst F/IV

[0052] The catalyst F/0 was pulverized and wetted with 1-octene. Thesample was then introduced into the measuring apparatus described aboveand heated under a nitrogen atmosphere. Tetragonal WO₃ was formed at atemperature as low as 400° C. (FIG. 2). This phase remains stable at 500and 600° C. In contrast to catalyst F/0, no transformation into themonoclinic phase occurred even after cooling to 200° C. It can beconcluded from this that the catalyst F/0 has been changed irreversiblyby the process of the present invention.

[0053] B. Metathesis Reactions

EXAMPLES 6-25

[0054] About 35 g of catalyst were placed in an electrically heated tubereactor. The temperature specified was set at the entrance to thecatalyst bed. A nonuniform temperature distribution of the heating ledto a rise in temperature through to the end of the catalyst bed (in eachcase reported in brackets). As feed pure 1-butene was fed in. Thereaction pressure was 9.7 bar. Analysis of the output from the reactorwas carried out on-line using a GC. Before the actual measurement, thecatalysts had each been activated by the specified procedure 0-VI. Theresults are shown in table 3. TABLE 3 1-Butene Cat./ T WHSV conversionHexenes Propenes C₆ selectivity Ex. meth. [° C.] h⁻¹ [%] Isomerization¹⁾[mol %] [mol %] [mol %] ²⁾  5 B/0 190 7.9 66.6 66.4 0 0 0 (comp.) (256) 6 C2/0 190 7.9 24.7 24.5 0 0 0 (comp.) (249)  7 D/0 190 7.6 43.6 43.4 00.1 0 (comp.) (268)  8 E1/0 190 8.0 60.3 59.9 0.1 0.2 0.2 (comp.) (263) 9 G/0 190 8.7 52.6 51.5 0.2 0.8 0.8 (comp.) (303) 10 H/0 190 7.8 79.979.6 0.1 0.3 0.1 (comp.) (269) 11 J/0 189 15.1 14.0 13.0 0.3 0.2 7.9(comp.) (242) 12 A/VII 189 8.0 65.7 49.3 6.3 7.7 19.3 (comp.) (274) 13C1/ 190 9.3 53.4 53.4 0 0 0 (comp.) VI (247) 14 B/I 190 8.1 77.4 76.00.4 1.4 0.9 (comp.) (280) 15 B/II 190 8.1 75.0 60.1 5.0 6.9 13.3 (comp.)(270) 16 B/III 190 8.1 62.4 43.1 7.8 9.6 24.9 (256) 17 A/III 189 8.063.0 32.7 11.5 16.1 36.4 (274) 18a C2/ 189 4.0 37.0 6.9 15.6 2.8 84.1III (208) 18b C2/ 190 6.0 32.5 5.7 12.8 2.1 78.5 III (231) 18c C2/ 1908.0 29.9 4.3 13.1 1.5 87.9 III (240) 19 D/III 200 7.6 47.8 11.5 16.8 7.870.3 (244) 20 E1/ 190 7.4 46.5 13.5 14.6 7.3 62.8 III (251) 21 E2/0 1907.7 43.5 23.0 8.7 7.4 40.0 (comp.) (228) 22 E2/ 190 7.2 47.0 12.8 16.66.5 70.5 III (228) 23a G/III 155 4.3 44.1 13.9 13.5 6.9 61.1 (238) 23bG/III 190 8.8 52.8 22.5 13.4 10.2 50.8 (293) 24 H/III 190 7.6 64.0 57.02.4 3.4 7.6 (263) 25a J/III 189 4.0 41.2 8.2 17.9 4.3 86.0 (212) 25bJ/III 190 10.0 33.9 6.1 15.1 2.8 86.7 (237) 25c J/III 190 14.9 38.7 4.816.7 2.6 86.3 (240) 25d J/III 170 14.9 26.9 2.5 13.3 1.1 98.9 (217) 26E1/ 190 7.7 43.2 14.8 12.2 6.9 56.7 IV (247) 27 B/V 190 7.7 64.5 38.410.1 13.5 31.2 (250)

We claim:
 1. A process for preparing a supported catalyst (catalyst C)comprising a support (support S) and an active component (activator A),wherein a) a catalyst precursor is prepared by applying an activatorcustomary for the catalysis of metathesis reactions (activatorprecursor) to a customary support (step a), b) the catalyst precursorprepared in step a) is brought into contact with a hydrocarbon compoundat from −20 to 550° C. (step b) and c) the catalyst precursor preparedin step b) is heated at from 410 to 850° C. in an inert gas atmosphere(step c).
 2. A process as claimed in claim 1, wherein the support (S) isselected from among oxides, phosphates, silicates, carbides, borides andnitrides of main group elements and elements of transition groups VI andII and mixtures of the abovementioned compounds.
 3. A process as claimedin either of the preceding claims, wherein the support (S) is selectedfrom the group consisting of Al₂O₃, aluminosilicates, Ga₂O₃, SiO₂, GeO₂,TiO₂, ZrO₂, SnO₂ and mixtures of the abovementioned compounds.
 4. Aprocess as claimed in any of the preceding claims, wherein the activatorprecursor comprises compounds containing elements of transition groupsV, VI and VII.
 5. A process as claimed in claim 4, wherein the compoundsof elements of transition groups V, VI and VII are selected from thegroup consisting of sulfides, oxides, nitrides, carbides, oxycarbides,carbonyls, organic complexes, halides, acids, polyacids, heteropolyacidsand salts of the acids, polyacids and heteropolyacids.
 6. A process asclaimed in any of the preceding claims, wherein the activator precursorcomprises compounds selected from the group consisting of rhenium,tungsten and molybdenum compounds.
 7. A process as claimed in any of thepreceding claims, wherein the activator precursor comprises compoundsselected from the group consisting of molybdenum oxides, tungstencarbides and tungsten oxides.
 8. A process as claimed in any of thepreceding claims, wherein the activator precursor comprises compoundsselected from the group consisting of compounds of metals of transitiongroups V, VI and VII and a promoter selected from the group consistingof cobalt, alkali metal and alkaline earth metal compounds.
 9. A processas claimed in any of the preceding claims, wherein step (a) is carriedout by impregnating the support (S) with a solution of the activatorprecursor and subsequently drying it and, if desired, calcining it. 10.A process as claimed in any of the preceding claims, wherein thehydrocarbon compound used in step (b) is selected from the groupconsisting of C₁-C₂₀-alkanes, -cycloalkanes, -olefins, -cycloolefins,-alkynes, -cycloalkynes, aromatics and mixtures of the abovementionedcompounds.
 11. A process as claimed in any of the preceding claims,wherein the inert gas used in step (c) is selected from the groupconsisting of nitrogen, carbon dioxide and noble gases and mixturesthereof.
 12. A catalyst (C) obtainable by a process as claimed in any ofclaims 1 to
 11. 13. A catalyst (C) as claimed in claim 12 comprisingfrom 0.1 to 30% by weight of WO₃ in tetragonal form.
 14. A catalyst (C)as claimed in claim 13, wherein the support S consists essentially ofSiO₂.
 15. A process for preparing unsaturated compounds by metathesisusing a catalyst (C).
 16. A process as claimed in claim 15, wherein3-hexene and ethylene are prepared by bringing 1-butene into contactwith a catalyst (C) at from 50 to 500° C.
 17. A process as claimed inclaim 11, wherein propene is prepared by bringing a mixture of 2-buteneswith ethylene or 1-butene into contact with a catalyst (C) at from 50 to500° C.